The invention relates to a method for attaching and securing power supply wires which are aligned parallel to one another to lateral surfaces of electrical components which are situated opposite one another. First, a taper- or strip-shaped transport carrier of an automatically functioning assembly system is continuously provided with current supply wires provided as one piece units in a U-shape and intended for a respective component. The two legs of the U-shape and the part connecting them project laterally beyond the edge of the transport carrier. Subsequently, the component is clamped between the legs and is then soldered to them.
Such a method is described in the German AS No. 21 38 083, incorporated herein by reference. However, the electrical component is thereby either inserted between the U-shaped connection wires perpendicular to the plane of said wires or, in case bends which could lead to the crossing of the connection wires are incorporated in the connection wires, the components are indeed inserted in the plane of the U-shape, but, however, in the direction of the displacement of the strip-shaped transport carrier.
During insertion of the components between the U-shaped portion perpendicular to its plane, a very precise adaptation of the path of the wire-shaped power leads for the component can lead to failures in the insertion. Therefore, insertion in the direction parallel to the displacement direction of the transport carrier requires additional steps in the automatically functioning assembly system when opening the crossing parts of the connection wires.
A method for attaching power connections to electrical components is described in German AS No. 11 53 807, incorporated herein by reference, in which the design of the power supplies and their fastening to the strip-shaped carrier strips are undertaken in such manner that the projecting, free ends guarantee a clamping effect. The components are secured between these free ends by means of this clamping effect. The power leads are then electrically conductively and mechanically secured to the components. The power leads intended for components to be built in are designed of one piece, i.e. in a hairpin shape.
This method is only suitable for the attachment and securing of power supply wires to electrical components which are disc-shaped and in which the power supply wires connect at the large lateral surfaces lying opposite one another.
A disc-shaped electrical impedance element with power supply leads and a method for attaching power supply leads to such an element is described in the German AS No. 11 62 011, incorporated herein by reference, in which the power supply leads follow the outline of the disc, approach one another up to a short distance, and then bend away from the disc edge together. An insulating ring is provided approximately at this location through which the wires pass and in which these wires are secured by means of part of a lacquer layer encapsulating the disc on all sides.
In this method, the power supply leads are attached to the narrow sides of a disc-shaped component which lie opposite one another. However, the method required for this type of attaching of power supply leads cannot be implemented with automatically functioning assembly systems in which a strip-shaped transport carrier is employed.
The term "electrical components" is employed within the framework of the present invention for electrical resistors, ceramic ptc resistors, electrical capacitors, particularly multi-layer capacitors with a ceramic dielectric. The term also applies in general for electrical components which have a body which is either itself part of the electrical component (capacitors, resistors, semiconductors) or serves as the carrier plate for other electrical components (for example printed layer circuits), whereby a respective power supply lead is to be secured to these carrier bodies at opposite sides.
In attaching and securing power supply leads to electrical components by means of automatically functioning assembly systems, the individual work steps must be dimensioned to cooperate with one another in such manner that a high clock time of the assembly system is rendered possible. The clock time (the turn "clock time" means the number of movements of the conveying band per minute) of the assembly system depends on the work step which involves the greatest time or, respectively, is difficult to execute. Whereas the shaping of the individual connection leads of a component into a U-shape, the insertion of said U-shape into slots of a transport carrier belt, the further shaping of these connection leads, the later soldering of said leads to the metal surfaces of the electrical component, the testing and the encapsulation with a protective layer are work steps which can be quickly carried out if need be by means of multiple subdivision, the insertion of the electrical component between the power supply leads and the temporary stoppage of said component until the soldering operation presents difficulties which lead to the fact that these work steps determine the overall clock time for the assembly system.
Added thereto is the fact that the electrical components do not always exhibit constant external dimensions, so that the insertion between the power supply leads presents difficulties for the temporary stop, for example, insofar as the required, temporary stop or halt is not guaranteed and an electrically conductive and mechanically stable connection, therefore, does not arise. When the electrical components which are to be provided with power supply leads have different dimensions because of their electrical requirements, then-even if it is only a matter of small differences-the system must always be readjusted. This, however, leads to standstill times, particularly given smaller unit numbers.